From the Guidelines
Abnormal red blood cell (RBC) morphology with normal MCV and MCH but elevated RDW suggests a mixed population of red blood cells with varying sizes, indicating possible early iron deficiency anemia, vitamin B12 or folate deficiency, or a combination of microcytic and macrocytic cells. This pattern can occur when a disease process is beginning and not all cells are affected yet, or when there are competing factors affecting red cell production 1. The elevated RDW indicates increased variation in red cell size (anisocytosis) while the normal MCV and MCH suggest that the average size and hemoglobin content of the cells remain within normal range.
Key Considerations
- The most common forms of anemia in patients with abnormal RBC morphology are iron deficiency anemia, anemia of chronic disease, and a combination of both 1.
- Vitamin B12 or folate deficiency, hemolytic anemia, and drug-induced anemia are less prevalent forms, but should also be considered 1.
- Anaemia should be investigated with red cell distribution width (RDW), mean corpuscular volume (MCV), reticulocyte count, full blood count (FBC), ferritin, transferrin saturation, and CRP levels 1.
Diagnostic Approach
- Further investigation should include a complete blood count with peripheral smear review, iron studies (ferritin, iron, TIBC), vitamin B12 and folate levels, and possibly hemoglobin electrophoresis if hemoglobinopathies are suspected 1.
- Reticulocyte count may also be helpful to assess bone marrow response 1.
- If the cause of anemia remains unclear, further laboratory tests should include B12, red cell folic acid, haptoglobin, and lactate dehydrogenase 1.
Treatment
- Treatment would depend on the underlying cause identified through these additional tests 1.
- Iron deficiency may be caused by continuous blood loss, malnutrition, or impaired iron uptake, and treatment should be tailored to the underlying cause 1.
From the Research
Abnormal RBC Morphology with Normal MCV and MCH, Elevated RDW
- Abnormal red blood cell (RBC) morphology can be associated with various anemic conditions, including iron deficiency anemia, vitamin B12 deficiency, and folate deficiency 2, 3, 4.
- A normal mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) with an elevated red blood cell distribution width (RDW) may indicate a mixed anemia or an early stage of anemia 5.
- RDW is a measure of the variation in RBC size, and an elevated RDW can indicate a significant variation in RBC size, which can be seen in iron deficiency anemia, vitamin B12 deficiency, and folate deficiency 2, 5, 3.
- The diagnosis of anemia and the underlying cause can be determined through a combination of laboratory tests, including a complete blood count, reticulocyte count, iron studies, and vitamin B12 and folate levels 2, 5, 3, 4, 6.
- Treatment of iron deficiency anemia with pharmacological iron can increase serum vitamin B12 and folate levels, even in patients with baseline low levels of serum vitamin B12 6.
- Healthcare practitioners should be aware of the changes in metabolic pathways, including vitamin B12, folate, and lipids, that can occur in iron deficiency anemia management 6.